1. Field of the Invention
This invention relates generally to fastener driving tools, in particular, to a battery operated fastener driving tool which uses the energy stored in a spring to drive the fastener.
2. Description of the Related Art
Many different types of tools have been developed over the years for the purpose of driving a fastener into wood. The most common type of fastener driving tool is the type in which the driver is actuated pneumatically. An example of this type of tool is shown in U.S. Pat. No. 3,278,106. While these tools work well, one drawback to their use is the requirement of a compressor to provide the pneumatic power.
In recent times, other designs for fastener driving tools have used electromechanical designs to provide the energy necessary to drive the fasteners. Some of these tools use a heavy duty solenoid to provide the driving force. Others employ the use of one or more flywheels to generate the necessary driving force. While these types of tools have been successful, it is necessary to use an electrical cord, instead of a pneumatic hose, to supply the driving power.
An alternative design has become popular which uses internal combustion to provide the motive force, thus allowing the tools to become truly portable, with no hose or cord necessary for the operation of the tool. An example of this type of tool is taught in U.S. Pat. No. 4,403,722. Although this type of tool has been successful, some drawbacks have been associated with internal combustion tools. First, the expense for operating these tools is higher than the pneumatic and electrical tools; in addition, the exhaust fumes from these tools can be bothersome when working in an enclosed area.
Some newer electric tools have been designed such that they can be operated using batteries. Examples of these types of tools can be seen in U.S. Pat. Nos. 6,607,111 and 6,669,072. When used with rechargeable batteries, theses tools are portable and can be operated at minimal cost. However, these tools are necessarily bulky and heavy, as they require high energy mechanisms to drive the fasteners.
U.S. Pat. No. 5,720,423 teaches a fastener driving tool which uses a drive piston within a gas chamber in which the piston is moved in a direction opposite the driving direction within the gas chamber to compress the gas above the piston such that the piston drives a fastener when released as a result of the compressed air. However, the size of this tool is dictated by the length of the gas chamber, as the gas must be compressed significantly to generate the force needed to drive larger fasteners, and it is also necessary to include an air replenishing tank to supply compressed air to the chamber when the pressure drops below a predetermined value.
Finally, other tools use linear compression springs as an energy storage device to provide the driving force needed to drive a fastener into a substrate. These springs do not adapt efficiently in a chamber to create a sufficient force to drive larger fasteners, and the springs generally do not have proper duty cycles, leading to premature failure.